1. Field of the Invention
The present invention relates to a magnetic sensor mounted in a hard disk drive or the like for reproduction, and more particularly to a magnetic sensor in which a resistance change rate (xcex94R/R) can be improved and magnetization control of a free magnetic layer can be satisfactorily performed.
2. Description of the Related Art
FIG. 26 is a partial sectional view of a structure of a conventional magnetic sensor, looking from a side facing a recording medium.
Numeral 14 shown in FIG. 26 denotes a barrier layer made of, e.g., Ta. An antiferromagnetic layer 30 made of, e.g., PtMn is formed on the barrier 14.
A pinned magnetic layer 31 of a magnetic material is formed on the antiferromagnetic layer 30. A nonmagnetic material layer 32 made of, e.g., Cu is formed on the pinned magnetic layer 31, and a free magnetic layer 33 is formed on the nonmagnetic material layer 32. The free magnetic layer 33 is of a multi-layered ferri-structure made up three layers, i.e., magnetic layers 37, 39 and a nonmagnetic intermediate layer 38. Note that, in the following description, the magnetic layer 37 on the side contacting the nonmagnetic material layer 32 is called a second magnetic layer and the magnetic layer 39 in an opposing relation to the second magnetic layer 37 with the nonmagnetic intermediate layer 38 interposed therebetween is called a first magnetic layer.
Further, as shown in FIG. 26, a barrier layer 7 made of, e.g., Ta is formed on the free magnetic layer 33.
A hard bias layer 5 is formed on each of both sides of multilayered films from the buffer layer 14 to the barrier layer 7 in the track-width direction (X-direction (positive and negative) shown in FIG. 26). An electrode layer 8 is formed on the hard bias layer 5.
In the magnetic sensor having such a structure, magnetization of the pinned magnetic layer 31 is fixed in the height direction (Y-direction shown in FIG. 26) by an exchange coupling magnetic field generated between the pinned magnetic layer 31 and the antiferromagnetic layer 30.
On the other hand, the second magnetic layer 37 and the first magnetic layer 39 both constituting the free magnetic layer 33 are magnetized antiparallel to each other in the track-width direction by a longitudinal bias magnetic field applied from the hard bias layer 5 and the RKKY interaction generated between the second magnetic layer 37 and the first magnetic layer 39. For example, when the second magnetic layer 37 is magnetized to the right in FIG. 26 (positive X-direction) in the track-width direction, the first magnetic layer 39 is magnetized to the left in FIG. 26 (opposed to the positive X-direction) in the track-width direction.
The second magnetic layer 37 and the first magnetic layer 39 both constituting the free magnetic layer 33 are, unlike the pinned magnetic layer 31, put into a weak single domain state in which magnetization is reversible in response to an external magnetic field. The electrical resistance of the free magnetic layer 33 is changed depending on the relationship between the direction of fixed magnetization of the pinned magnetic layer 31 and the direction of magnetization of the free material layer 33 affected by the external magnetic field. An external signal from a recording medium is reproduced in accordance with a voltage change caused upon a change of the electrical resistance.
When the free magnetic layer 33 is of the multilayered ferri-structure as shown in FIG. 26, the layer that actually contributes to the magnetoresistive effect is the second magnetic layer 37.
Accordingly, when a sensing current flows from the electrode layer 8 primarily to the nonmagnetic material layer 32, there occurs a shunt loss if the sensing current is shunted to the first magnetic layer 39, thus resulting in a reduction of the resistance change rate (xcex94R/R).
To reduce such a shunt loss, it has been proposed to increase the specific resistance of the first magnetic layer 39, for example, by adding Cr to the first magnetic layer 39 which has been so far formed of a CoFe alloy or the like. That proposal has, however, invited deterioration of reproduction characteristics, such as lowering of a reproduction output and the occurrence of noises, because the increased specific resistance of the first magnetic layer 39 reduces the coupling magnetic field based on the RKKY interaction generated between the second magnetic layer 37 and the first magnetic layer 39 to such an extent that the second magnetic layer 37 and the first magnetic layer 39 both constituting the free magnetic layer 33 cannot be satisfactorily magnetized in the antiparallel state.
FIG. 27 is a partial sectional view of another conventional magnetic sensor having a different structure, looking from a side facing a recording medium. In FIG. 27, the same numerals as those in FIG. 26 represent the same layers as those in FIG. 26.
In the magnetic sensor of FIG. 27, as with that of FIG. 26, a free magnetic layer 33 is of a multi-layered ferri-structure in which a nonmagnetic intermediate layer 38 is interposed between two magnetic layers 37 and 39. In the structure of FIG. 27, however, antiferromagnetic layers 40 are formed on the first magnetic layer 39 of the free magnetic layer 33 with a predetermined spacing left between the antiferromagnetic layers 40 in the track-width direction (X-direction). The method of controlling magnetization of the free magnetic layer 33 using the antiferromagnetic layers 40, as shown in FIG. 27, is called an exchange biasing method.
In the structure of FIG. 27, when an exchange coupling magnetic field is generated between the antiferromagnetic layers 40 and both end portions A of the first magnetic layer 39 and magnetization in both the end portions A of the first magnetic layer 39 is fixed, e.g., to the right in FIG. 27 (positive X-direction) in the track-width direction, magnetization in both end portions A of the second magnetic layer 37 formed in an opposing relation to the first magnetic layer 39 with the nonmagnetic intermediate layer 38 interposed therebetween is fixed to the left in FIG. 26 (opposed to the positive X-direction) in the track-width direction by a coupling magnetic field based on the RKKY interaction generated between the second magnetic layer 37 and the first magnetic layer 39.
In a central portion B of the free magnetic layer 33, the second magnetic layer 37 and the first magnetic layer 39 are also magnetized in the antiparallel state, but they are put into a weak single domain state in which magnetization is reversible in response to an external magnetic field.
That magnetic sensor employing the exchange biasing method also has the problems as with the magnetic sensor of FIG. 26. Specifically, when the first magnetic layer 39 constituting the free magnetic layer 33 is formed of a CoFe alloy, the resistance change rate (xcex94R/R) is reduced with shunting of the sensing current. Further, when the first magnetic layer 39 is formed of a CoFeCr alloy, lowering of the unidirectional exchange bias magnetic field (Hex*) becomes noticeable.
Herein, the term xe2x80x9cunidirectional exchange bias magnetic field (Hex*)xe2x80x3 represents a resultant magnetic field of an exchange coupling magnetic field (Hex) primarily generated between the antiferromagnetic layers 40 and the first magnetic layer 39 and a coupling magnetic field based on the RKKY interaction generated between the first magnetic layer 39 and the second magnetic layer 37.
FIG. 28 is a graph showing the relationship between a film thickness of the first magnetic layer 39 and a unidirectional exchange bias magnetic field (Hex*) resulting when the first magnetic layer 39 is formed of CoFe or CoFeCr5 at % in a magnetic sensor having the same multilayered structure as that shown in FIG. 27.
As seen from FIG. 28, when the first magnetic layer 39 is formed of a CoFe alloy, the unidirectional exchange bias magnetic field (Hex*) has a very high value. However, when the first magnetic layer 39 is formed of a CoFeCr alloy, the unidirectional exchange bias magnetic field is sharply reduced.
Also, as seen from FIG. 28, there is a tendency that as the film thickness of the first magnetic layer 39 made of CoFeCr increases, the unidirectional exchange bias magnetic field (Hex*) is also increased. However, a greater thickness of the first magnetic layer 39 increases the amount of the sensing current shunted to the first magnetic layer 39. Eventually, it has been impossible in the past to improve both the unidirectional exchange bias magnetic field (Hex*) and the resistance change rate (xcex94R/R) in the free magnetic layer 33 at the same time.
With the view of solving the above-stated problems in the related art, it is an object of the present invention to provide a magnetic sensor, which has an improved film makeup of a first magnetic layer of a free magnetic layer having a multilayered ferri-structure, and which can improve the resistance change rate (xcex94R/R), increase the unidirectional exchange bias magnetic field (Hex*), and satisfactorily control magnetization of the free magnetic layer.
To achieve the above object, according to a first aspect of the present invention, there is provided a magnetic sensor including a laminate comprising an antiferromagnetic layer, a pinned magnetic layer formed in contact with the antiferromagnetic layer, and a free magnetic layer formed in an opposing relation to the pinned magnetic layer with a nonmagnetic material layer interposed between the free magnetic layer and the pinned magnetic layer, wherein the free magnetic layer is of a multilayered ferri-structure comprising a second magnetic layer formed in contact with an interface between the free magnetic layer and the nonmagnetic material layer, and a first magnetic layer formed in an opposing relation to the second magnetic layer with a nonmagnetic intermediate layer interposed therebetween, and wherein the first magnetic layer includes an area which contains an element X (X represents at least one element selected from among Cr, Ti, V, Zr, Nb, Mo, Hf, Ta and W) and which is present in position toward a side of the nonmagnetic intermediate layer from a side near an opposite surface of the first magnetic layer away from an interface between the first magnetic layer and the nonmagnetic intermediate layer, and an area which is partly located in a region from the interface between the first magnetic layer and the nonmagnetic intermediate layer toward the opposite surface of the first magnetic layer and which does not contain the element X.
In the above magnetic sensor, preferably, the first magnetic layer is formed primarily of a CoFe alloy, the area containing the element X is formed of a CoFeX alloy, and the area not containing the element X is formed of a CoFe alloy.
As an alternative, preferably, the first magnetic layer is formed primarily of a CoFeNi alloy, the area containing the element X is formed of a CoFeNiX alloy, and the area not containing the element X is formed of a CoFeNi alloy.
Thus, according to the first aspect of the present invention, the area containing the element X is present on the side nearer to the opposite surface of the first magnetic layer of the free magnetic layer having the multilayered ferri-structure, which is positioned away from the interface between the first magnetic layer and the nonmagnetic intermediate layer, and the area not containing the element X is present on the side nearer to the nonmagnetic intermediate layer.
The magnetic area containing the element X has a higher specific resistance than the magnetic area not containing the element X.
Hence, since the area containing the element X and having a high specific resistance is present in the first magnetic layer, the loss of a sensing current shunted to the first magnetic layer can be reduced in comparison with the case forming the first magnetic layer of only a magnetic material not containing the element X.
Further, according to the first aspect of the present invention, the element X is contained not over the entire area of the first magnetic layer and the area not containing the element X is present on the side nearer to the interface between the first magnetic layer and the nonmagnetic intermediate layer. From experiments described later, it was confirmed that the presence of the area not containing the element X on the side nearer to the interface between the first magnetic layer and the nonmagnetic intermediate layer increases a coupling magnetic field based on the RKKY interaction generated between the first magnetic layer and the second magnetic layer.
Consequently, according to the first aspect of the present invention, the resistance change rate (xcex94R/R) of the magnetic sensor can be increased in comparison with that obtained with the related art. In addition, it is possible to increase the coupling magnetic field based on the RKKY interaction generated between the first magnetic layer and the second magnetic layer both constituting the first magnetic layer, to satisfactorily control magnetization of the free magnetic layer, and to manufacture a magnetic sensor having superior reproduction characteristics.
According to a second aspect of the present invention, there is provided a magnetic sensor including a laminate comprising an antiferromagnetic layer, a pinned magnetic layer formed in contact with the antiferromagnetic layer, and a free magnetic layer formed in an opposing relation to the pinned magnetic layer with a nonmagnetic material layer interposed between the free magnetic layer and the pinned magnetic layer, wherein the free magnetic layer is of a multilayered ferri-structure comprising a second magnetic layer formed in contact with an interface between the free magnetic layer and the nonmagnetic material layer, and a first magnetic layer formed in an opposing relation to the second magnetic layer with a nonmagnetic intermediate layer interposed therebetween, wherein the first magnetic layer contains an element X (X represents at least one element selected from among Cr, Ti, V, Zr, Nb, Mo, Hf, Ta and W) when formed, and wherein the element X has a larger content on a side near an opposite surface of the first magnetic layer away from an interface between the first magnetic layer and the nonmagnetic intermediate layer than at the interface between the first magnetic layer and the nonmagnetic intermediate layer.
In the above magnetic sensor, preferably, the first magnetic layer is formed of a magnetic material made of a CoFe alloy and containing the element X.
As an alternative, preferably, the first magnetic layer is formed of a magnetic material made of a CoFeNi alloy and containing the element X.
Further, preferably, the content of the element X on the side near the opposite surface of the first magnetic layer away from the interface between the first magnetic layer and the nonmagnetic intermediate layer is not smaller than 3 at % but not larger than 15 at %.
According to the second aspect of the present invention, the element X is contained on the side near the interface between the first magnetic layer and the nonmagnetic intermediate layer as well, but its content is very small. Then, the content of the element X is adjusted such that it takes a higher value on the side nearer to the opposite surface of the first magnetic layer away from the interface between the first magnetic layer and the nonmagnetic intermediate layer.
As with the first aspect, according to the second aspect of the present invention, the specific resistance value of the first magnetic layer can be increased and the shunt loss of a sensing current can be reduced. Further, the coupling magnetic field based on the RKKY interaction generated between the first magnetic layer and the second magnetic layer can be increased.
Hence, according to the second aspect of the present invention, the resistance change rate (xcex94R/R) of the magnetic sensor can be increased in comparison with that obtained with the related art. In addition, it is possible to increase the coupling magnetic field based on the RKKY interaction generated between the first magnetic layer and the second magnetic layer both constituting the first magnetic layer, to satisfactorily control magnetization of the free magnetic layer, and to manufacture a magnetic sensor having superior reproduction characteristics.
In the above magnetic sensor, preferably, the first magnetic layer includes an area in which the content of the element X gradually decreases toward the interface between the first magnetic layer and the nonmagnetic intermediate layer from the side near the opposite surface of the first magnetic layer away from the interface between the first magnetic layer and the nonmagnetic intermediate layer.
The presence of such an area means that the so-called composition modulation occurs in the first magnetic layer. The occurrence of the composition modulation is attributable to a manufacturing method described later.
According to a third aspect of the present invention, there is provided a magnetic sensor including a laminate comprising an antiferromagnetic layer, a pinned magnetic layer formed in contact with the antiferromagnetic layer, and a free magnetic layer formed in an opposing relation to the pinned magnetic layer with a nonmagnetic material layer interposed between the free magnetic layer and the pinned magnetic layer, wherein the free magnetic layer is of a multilayered ferri-structure comprising a second magnetic layer formed in contact with an interface between the free magnetic layer and the nonmagnetic material layer, and a first magnetic layer formed in an opposing relation to the second magnetic layer with a nonmagnetic intermediate layer interposed therebetween, and wherein the first magnetic layer is made up of at least two magnetic layers, one of the two magnetic layers, which is positioned on a side near an opposite surface of the first magnetic layer away from an interface between the first magnetic layer and the nonmagnetic intermediate layer, being formed of a magnetic material containing an element X (X represents at least one element selected from among Cr, Ti, V, Zr, Nb, Mo, Hf, Ta and W), the other of the two magnetic layers, which is positioned on a side contacting the interface between the first magnetic layer and the nonmagnetic intermediate layer, being formed of a magnetic material not containing the element X.
In the above magnetic sensor, preferably, of the two magnetic layers, the one positioned on the side near the opposite surface of the first magnetic layer away from the interface between the first magnetic layer and the nonmagnetic intermediate layer is formed of a CoFeX alloy, and the other positioned on the side contacting the interface between the first magnetic layer and the nonmagnetic intermediate layer is formed of a CoFe alloy.
As an alternative, preferably, of the two magnetic layers, the one positioned on the side near the opposite surface of the first magnetic layer away from the interface between the first magnetic layer and the nonmagnetic intermediate layer is formed of a CoFeNiX alloy, and the other positioned on the side contacting the interface between the first magnetic layer and the nonmagnetic intermediate layer is formed of a CoFeNi alloy.
According to the third aspect of the present invention, the first magnetic layer of the free magnetic layer having the multilayered ferri-structure is made up of at least two magnetic layers. Of the at least two magnetic layers, one positioned on the side near the opposite surface of the first magnetic layer away from the interface between the first magnetic layer and the nonmagnetic intermediate layer is formed of a magnetic material containing the element X and having a high specific resistance value. Thus, since the magnetic area having a high specific resistance value is present in the first magnetic layer, the loss of a sensing current shunted to the first magnetic layer can be reduced and the resistance change rate (xcex94R/R) can be improved.
On the other hand, the magnetic layer on the side contacting the nonmagnetic intermediate layer is formed of a magnetic material not containing the element X. This increases a coupling magnetic field based on the RKKY interaction generated between the magnetic layer on the side contacting the nonmagnetic intermediate layer and the second magnetic layer.
Consequently, according to the third aspect of the present invention, the resistance change rate (xcex94R/R) of the magnetic sensor can be increased in comparison with that obtained with the related art. In addition, it is possible to increase the coupling magnetic field based on the RKKY interaction generated between the first magnetic layer and the second magnetic layer both constituting the first magnetic layer, to satisfactorily control magnetization of the free magnetic layer, and to manufacture a magnetic sensor having superior reproduction characteristics.
In the present invention, preferably, when the area containing the element X is formed of a CoFeX alloy or a CoFeNiX alloy and the area not containing the element X is formed of a CoFe alloy or a CoFeNi alloy, a film thickness ratio of (film thickness of the CoFeX alloy/film thickness of the first magnetic layer) or of (film thickness of the CoFeNiX alloy/film thickness of the first magnetic layer) is larger than 0 but not larger than 0.61.
As an alternative, preferably, when the area containing the element X is formed of a CoFeX alloy or a CoFeNiX alloy and the area not containing the element X is formed of a CoFe alloy or a CoFeNi alloy, a film thickness ratio of (film thickness of the CoFeX alloy/film thickness of the first magnetic layer) or of (film thickness of the CoFeNiX alloy/film thickness of the first magnetic layer) is larger than 0 but not larger than 0.36.
As an alternative, preferably, when the area containing the element X is formed of a CoFeX alloy or a CoFeNiX alloy and the area not containing the element X is formed of a CoFe alloy or a CoFeNi alloy, a film thickness ratio of (film thickness of the CoFeX alloy/film thickness of the first magnetic layer) or of (film thickness of the CoFeNiX alloy/film thickness of the first magnetic layer) is not smaller than 0.26 but not larger than 0.82.
As an alternative, preferably, when the area containing the element X is formed of a CoFeX alloy or a CoFeNiX alloy and the area not containing the element X is formed of a CoFe alloy or a CoFeNi alloy, a film thickness ratio of (film thickness of the CoFeX alloy/film thickness of the first magnetic layer) or of (film thickness of the CoFeNiX alloy/film thickness of the first magnetic layer) is not smaller than 0.12 but not larger than 0.61.
As an alternative, preferably, when the area containing the element X is formed of a CoFeX alloy or a CoFeNiX alloy and the area not containing the element X is formed of a CoFe alloy or a CoFeNi alloy, a film thickness ratio of (film thickness of the CoFeX alloy/film thickness of the first magnetic layer) or of (film thickness of the CoFeNiX alloy/film thickness of the first magnetic layer) is not smaller than 0.26 but not larger than 0.61.
As an alternative, preferably, when the area containing the element X is formed of a CoFeX alloy or a CoFeNiX alloy and the area not containing the element X is formed of a CoFe alloy or a CoFeNi alloy, a film thickness ratio of (film thickness of the CoFeX alloy/film thickness of the first magnetic layer) or of (film thickness of the CoFeNiX alloy/film thickness of the first magnetic layer) is not smaller than 0.26 but not larger than 0.36.
Further, in the present invention, a composition ratio of the element X is preferably not smaller than 3 at % but not larger than 15 at %.
Still further, in the present invention, when the magnetic layer is formed of CoFe, CoFeX, CoFeNi or CoFeNiX, an atomic percentage Y of CoY and Fe100xe2x88x92Y is preferably not smaller than 85% but not larger than 96%.
Still further, in the present invention, when the magnetic layer is formed of CoFeNi or CoFeNiX, a composition ratio of Ni is preferably not smaller than 0.5 at % but not larger than 5 at %.
Moreover, in the present invention, it is preferable that second antiferromagnetic layers are disposed on the side near the opposite surface of the first magnetic layer away from the interface between the first magnetic layer and the nonmagnetic intermediate layer with a predetermined spacing left between the second antiferromagnetic layers in a track-width direction. This feature represents a structure for controlling magnetization of the free magnetic layer by the so-called exchange biasing method.
From experiments described later, it was confirmed that with the presence of the magnetic area containing the element X in the first magnetic layer on the side nearer to an interface between the first magnetic layer and the second antiferromagnetic layer, an exchange coupling magnetic field (Hex) generated between the magnetic layer containing the element X and the second antiferromagnetic layer is increased from that obtained in the case forming the magnetic area not containing the element X on the side nearer to the interface between the first magnetic layer and the second antiferromagnetic layer.
Also, as stated above, the coupling magnetic field based on the RKKY interaction generated between the upper (first) and lower (second) magnetic layers with the nonmagnetic intermediate layer interposed therebetween is increased with the presence of the magnetic area not containing the element X on the side nearer to the interface between the first magnetic layer and the second magnetic layer in comparison with that obtained in the case forming the magnetic area containing the element X on the side nearer to the interface between the first magnetic layer and the second magnetic layer.
Consequently, in the present invention, by forming, in the first magnetic layer, the magnetic area containing the element X on the side nearer to the interface between the first magnetic layer and the second antiferromagnetic layer and the magnetic area not containing the element X on the side nearer to the interface between the first magnetic layer and the second magnetic layer, the shunt loss of a sensing current can be suppressed and the resistance change rate can be increased. In addition, it is possible to increase both the exchange coupling magnetic field (Hex) generated between the first magnetic layer and the second antiferromagnetic layer and the coupling magnetic field based on the RKKY interaction. Hence, a unidirectional exchange bias magnetic field (Hex*) in the first magnetic layer can be satisfactorily increased from that obtained with the related art.
Thus, in the structure in which magnetization of the free magnetic layer is controlled by the exchange biasing method, the resistance change rate can be increased from that obtained with the related art. In addition, it is possible to satisfactorily control magnetization of the free magnetic layer, and to manufacture a magnetic sensor having superior reproduction characteristics.
In the present invention, bias layers may be disposed on both sides of the free magnetic layer in a track-width direction.
Also, the present invention may be implemented such that an electrode layer is disposed on a side near an opposite surface of each of the second antiferromagnetic layers away from an interface between the second antiferromagnetic layer and the first magnetic layer, and an electrical current flows in a direction parallel to a film surface of each layer of the laminate. As another embodiment, electrode layers may be disposed on the bias layers and an electrical current may flow in a direction parallel to a film surface of each layer of the laminate.
A magnetic sensor in which an electrical current flows in the direction parallel to the film surface of each layer of the magnetic sensor is called a CIP (current in the plane) type magnetic sensor.
Alternatively, the present invention may be implemented such that electrode layers are disposed on and under the magnetic sensor, and an electrical current flows in a direction perpendicular to a film surface of each layer of the laminate. Such a magnetic sensor is called a CPP (current perpendicular to the plane) type magnetic sensor.
In the case of the CPP type magnetic sensor, preferably, the upper electrode layer disposed on the laminate is an upper shield layer formed of a magnetic material. It is therefore possible to facilitate manufacture of the magnetic sensor, to shorten the gap length G1, and to manufacture a magnetic sensor satisfactorily adaptable for a higher recording density.
In that magnetic sensor, preferably, the free magnetic layer is formed on an upper side of the antiferromagnetic layer and second antiferromagnetic layers are disposed on the first magnetic layer constituting the free magnetic layer with a predetermined spacing left between the second antiferromagnetic layers in a track-width direction; first insulating layers are disposed on the second antiferromagnetic layers and second insulating layers are disposed on inner end surfaces of both the second antiferromagnetic layers and the first insulating layers; and the upper electrode layer is formed to cover the first insulating layers and the second insulating layers and to fill the spacing left between the second antiferromagnetic layers. With that feature, the current flowing from the upper electrode layer into the laminate is satisfactorily avoided from being shunted to the second antiferromagnetic layer, and a magnetic sensor can be manufactured which can provide a greater reproduction output, has a narrower effective reproduction track width, and is suitable for a higher recording density.
In the present invention, preferably, the first insulating layers and the second insulating layers are formed separately from each other.
Further, in the case of the CPP type magnetic sensor, the lower electrode layer disposed under the laminate is preferably a lower shield layer formed of a magnetic material. With that feature, it is possible to facilitate manufacture of the magnetic sensor, to shorten the gap length G1, and to manufacture a magnetic sensor satisfactorily adaptable for a higher recording density.
In the above magnetic sensor, preferably, the free magnetic layer is formed on an upper side of the antiferromagnetic layer and second antiferromagnetic layers are disposed on the first magnetic layer constituting the free magnetic layer with a predetermined spacing left between the second antiferromagnetic layers in a track-width direction; and a projection projecting in a multilayered direction of the laminate is formed at a center of the lower electrode layer in the track-width direction, the projection having an upper surface contacting a lower surface of the laminate, and insulating layers are disposed between both end portions of the lower electrode layer in the track-width direction and the laminate. With those features, the current flowing from the lower electrode layer into the laminate is hard to spread beyond the track width and the shunt loss of that current can be suppressed. Hence, it is possible to manufacture a magnetic sensor that can provide a greater reproduction output and has a narrower effective reproduction track width.
In the present invention, preferably, the upper surface of the projection and upper surfaces of the insulating layers disposed on both the end portions of the lower electrode layer are flush with each other.
Moreover, in the present invention, the nonmagnetic material layer is preferably formed of a nonmagnetic electrically conductive material. Such a magnetic sensor in which the nonmagnetic material layer is formed of a nonmagnetic electrically conductive material is called a spin-valve GMR type magnetoresistive sensor (CIP-GMR or CPP-GMR).
Additionally, the nonmagnetic material layer may be formed of an insulating material. Such a magnetic sensor is called a spin-valve tunneling type magnetoresistive sensor (CPP-TMR).